Blackett P M, Buckton G
Centre for Materials Science, School of Pharmacy, University of London.
Pharm Res. 1995 Nov;12(11):1689-93. doi: 10.1023/a:1016257504115.
The purpose of the work is to study the adsorption of Oleic acid and Span 85 (materials frequently used in aerosols as surfactants) onto partially amorphous and essentially crystalline salbutamol sulphate, attempting to understand the behaviour of metered dose inhalers (MDIs) and observing whether there were any differences in adsorption behaviour and if this could be related to the surface properties of the powder.
Isothermal titration microcalorimetry was the principal technique used to measure the adsorption behaviour of surfactants to salbutamol sulphate. A Malvern particle size analyzer was also employed to provide size data on the interactions between the surfactant and powder suspensions.
The calorimetric data revealed that surfactant adsorption to the crystalline micronised powder (78% RH and aged dry sample) produced significant exotherms, whereas adsorption to the partially amorphous micronised powder resulted in small heat responses. The differences in adsorption behaviour to the partially crystalline and crystalline surfaces resulted in changes in aggregation behaviour.
The stability of MDIs varies depending on the water content, crystallinity and surface composition of the powder. The advantages of using isothermal titration microcalorimetry to evaluate this surface behaviour in such difficult systems was demonstrated.
本研究旨在探讨油酸和司盘85（气雾剂中常用的表面活性剂）在部分无定形和基本结晶的硫酸沙丁胺醇上的吸附情况，试图了解定量吸入器（MDIs）的行为，并观察吸附行为是否存在差异，以及这是否与粉末的表面性质有关。
等温滴定量热法是用于测量表面活性剂对硫酸沙丁胺醇吸附行为的主要技术。还使用马尔文粒度分析仪提供表面活性剂与粉末悬浮液之间相互作用的粒度数据。
量热数据表明，表面活性剂吸附到结晶微粉化粉末（78%相对湿度和老化干燥样品）上会产生显著的放热，而吸附到部分无定形微粉化粉末上则产生较小的热响应。对部分结晶和结晶表面的吸附行为差异导致了聚集行为的变化。
MDIs的稳定性因粉末的含水量、结晶度和表面组成而异。证明了使用等温滴定量热法评估此类复杂体系中这种表面行为的优势。
